Hi, and welcome to the forum.

Until and unless the visa rules change, it will be considerably easier for your company to manage a transfer for you if you're at a manager level in the company.

But a good way to get your name on the short list for any transfers that do open up is to volunteer to work with any Americans (or any foreigners) visiting in your part of the company. Make yourself available to show visitors around or to take them out in the evenings while they're in town. Answer their questions and they'll be happy to talk to you about what sorts of jobs are available in the Milwaukee site.

It probably won't happen overnight, but if you can get yourself "known" to the folks over there (and known as someone who is sharp, a good worker and eager to learn) it could come around when there's an opening. (It's sort of how I got my first job overseas.)
Cheers,
Bev