The issue is that what OP wants to do (hop back and forth) is not really a circumstance the system has a good answer for. Upside is that there are multiple options available that each accommodate (a part) of what you want to achieve. Plenty have been mentioned by other’s here but I’d like to opt for a slightly different option.
In my opinion it would be best if you’d go live in Germany and while living there apply for your spouse’s green card with the consulate in Frankfurt through DCF (assuming the sponsorship requirements can be met). After that you’ll formally reside in the US and be US residents. There’s no need for them to apply for citizenship, the green card will give them access to the US.
The issue with a B visa and VWP is that there’s no guaranteed entry and it takes one denial to get a potential ban whereas a green card will pretty much guarantee you entry.
Some caveats:
I’d advice to try and not stay outside of the US longer than 179 days at a time. Not because like some people here are saying that you’ll lose the green card after 6 months, but because before the six months the LPR is not considered to be applying for admission, this is a technical matter but it basically boils down to being scrutinised at the border without a guarantee of being admitted.
If you are outside of the US longer than 180 days, at return if asked always emphasise that your trip outside of the US was temporary and that your regular place of abode is in the US. Make sure that during your absence you actually have a place of abode that you have free access to.
Try to ensure that each calendar year you’re more in the US than abroad (doesn’t have to be continuous).
If you are going to be outside of the US for a year or longer then apply for a reentry permit with form I-131, a SB-1 Returning Resident Visa at the consulate abroad or (not advised) apply at the port of entry with the CBP officer for a waiver.
Just know that there are no hard rules on this, no hard time lines (just in terms of scrutiny), CBP cannot take away your green card, they can only refer you to an immigration court. What CBP is known of doing, is asking you to sign a form that will have you abandon your LPR status, if that happens don’t sign. There are also no hard definition on what a temporary visit is. The Court of Appeals for the Ninth Circuit has tried to make it a bit less ephemeral, but the gist of is that the point needs to be that it’s as temporary travel outside of the US with the intention of coming back and officially domicile in the US. Also always file your US taxes (and figure out if you can elect the US to pay your taxes given the more beneficial rate compared to DE).
But good luck in your endeavours becoming global citizens.
DrivewayCali got a reaction from SalishSea in Traveling with no intention to immigrate