My concerns are:
I'll end up paying additonal income tax to the US government on my hard earned money.
The house my wife and I bought is now worth $270k more than we paid for it. We want to sell and move somewhere else, but I've heard the IRS will tax us capital gains on it. I'm not sure if I can tell them only half the profit is mine (the other half is my wife's)?
I have a bit of savings now and I was going to put some away in ISAs (like stocks and shares ISAs), but I've read this is a nightmare for UK/US citizens and investing my savings is going to become really difficult for me now.
I'm sure this is all standard stuff for most people, especially for 'real' Americans who emigrated to the UK, but I'm worried that I've opened Pandora's box and, finacially speaking, my life is about to get immeasurably worse. All the fear mongering has me convinced if I didn't go through with this I will be a fugitive from the law whose days are numbered.
Am I worrying over nothing? Or should I brace myself for a difficult road ahead?
As a US passport holder I think it would only be a matter of time before the US caught up with you so I think it is better to comply with US law now.
My wife and I are also Naturalized US citizens who returned to live in England and we file taxes in both countries.
When filing our US tax return we claim foreign tax credits against our US taxes for the taxes we pay to HMRC so we end up paying zero US taxes as the UK taxes we pay are higher than the US, on the same income - we have both US and UK pensions. Our son is in a similar situation.
You are correct about stocks and shares ISAs, if you invest in them, you can have them in your wife’s name if she is a UK citizen only as her income is not subject to US taxes.
Half ownership of your house and capital gain is easy to calculate, and since it is your primary residence you should be under the US $250k capital gain allowance on your primary residence. Note however that the calculation on that capital gain is more complicated than you may think as it must factor in the exchange rate to $s at time of purchase and sale plus similar forex gains or losses on a mortgage when you pay it off. Those calculations are definitely above my pay rate, I just know they exist.