By default, the TOC should pick up any paragraph formatted in a style
with an outline level specified (this includes the built-in heading
styles, regardless of their language-specific names). In other words,
transferring styles between countries should not be a problem, as long
as you use the default settings or simply add more levels of headings
in the Index and Tables dialog box.

Some changes do cause trouble, though. I know of one specific instance
(perhaps there are more) when Word inserts the \t switch and
explicitly specifies TOC levels (even if you use heading styles),
namely, if you use the Index and Tables dialog box to omit the Title
style (in Swedish: "Rubrik", could it be "Overskrift" in Norwegian?),
from your TOC.

The problem won't be apparent until the document is opened in a
different language version, when the TOC field cannot find a certain
built-in style, because the \t switch uses a localized version of its
name.  :-(

You can prepare the document template by making sure that only
"allowed" styles have an outline level. Here's how: In the Modify
Style dialog box: Click Format>Paragraph, and change the Outline Level
to the appropriate level or to "Body Text" (on the Indents and Spacing
tab).

Once styles are correctly setup with the outline level set (or
cleared), you can modify the TOC field code to read: { TOC \o "1-9"
\h }. This means that it will pick up only paragraphs whose style have
an outline level specified.

What's possible depends on your how much your users/co-workers know
about Word. Perhaps you don't expect them to modify TOC field codes.
In such a case, using custom styles could be an easier approach, and
the \t switch won't cause trouble. The down-side is of course that you
would lose some of the power attached to the built-in heading styles.