I need to change the format for all dates displayed in the properties tab of each node ... the created, last published, and last edited dates, etc ... to American style of mm/dd/yyyy.
Umbraco 4.7.1, IIS 7.5

It seems like it shouldn't be that hard, but we've spent a day and half on it and haven't made much progress.

1. <globalization>

I changed 

<globalization requestEncoding="UTF-8" responseEncoding="UTF-8" />

to

<globalization requestEncoding="UTF-8" responseEncoding="UTF-8" uiCulture="en-US" culture="en" /> 

and

<globalization requestEncoding="UTF-8" responseEncoding="UTF-8" uiCulture="auto" culture="auto" />

but no change.

2. en.xml

As per these promising instructions, I changed the first line in /umbraco/config/lang/en.xml from

<language alias="en" intName="English (uk)" localName="English" lcid="" culture="en-GB">

to

<language alias="en" intName="English (us)" localName="English" lcid="" culture="en-US">

which immediately resulted in almost all nodes of a document type that uses Richtext Editor/TinyMCE, which is almost all nodes in the site, to blow up (although the date format did correctly change for nodes of a document type that doesn't have TinyMCE):

Server Error in '/' Application.

String was not recognized as a valid DateTime.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.FormatException: String was not recognized as a valid DateTime.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 


[FormatException: String was not recognized as a valid DateTime.]
   System.DateTime.Parse(String s) +6364770
   uHidesy.Umbraco.usercontrols.uHidesy.uHidesy.LoadSettings() in D:\_PROJECTS\uHidesy - Property Hider\Branches\1.13_noDesc\Umbraco.Web\usercontrols\uHidesy\uHidesy.ascx.cs:102
   uHidesy.Umbraco.usercontrols.uHidesy.uHidesy.OnLoad(EventArgs e) in D:\_PROJECTS\uHidesy - Property Hider\Branches\1.13_noDesc\Umbraco.Web\usercontrols\uHidesy\uHidesy.ascx.cs:44
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3064

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.272

although new nodes seem to work alright.

Next, I made a new /umbraco/config/lang/en.xml, name it us.xml, and changed

<language alias="en" intName="English (uk)" localName="English" lcid="" culture="en-GB">

to 

<language alias="us" intName="English (us)" localName="English" lcid="" culture="en-US">

then changed a user's language to English (us) and got similar results.

If I create a new node (of a document type with TinyMCE) while using culture="en-US", it breaks almost all nodes (of a document type with TinyMCE) permanently, if even I switch back to culture="en-GB".

3. Richtext Editor/TinyMCE

In the previously-mentioned promising instructions, Immo Wache indicates that several files need to be changed to update TinyMCE. I changed them all according to the plan, upon starting this whole process over for a second time found even more .js files than listed, and with culture="en-US" being used in conjunction with the creation of a new nodes (of a document type which uses TinyMCE), previous nodes break again with the same error. 

4. My current thoughts

First off, why is this so hard? Second, since I do get favorable results for nodes of a document type that doesn't have TinyMCE, it seems like I'm on the right track if I can get TinyMCE to work around this. I can go back and forth with culture="" and un-break the 'String was not recognized as a valid DateTime' error,  but once I create a new article under the culture="en-US" everything breaks to the point that I have to restore a backup from two days ago. I'm also thining about the date picker with time datatype.

Do you see anything I missed above? Any help would be DEEPLY appreciated.