With some exceptions, generally your good or bad credit does not follow you around the world.
In general, this. However, I don't think anyone on here can say with any certainty whether/if/how much bad credit will affect your immigration process over time. If we knew of actual cases where it has happened, that would be one thing. But as far as I know, we don't.
online_girl, if I were you, I wouldn't be asking a forum like this for advice on this particular matter. At best, we are armchair advisers on it (any advice to be taken with a grain of salt), and if you want to address the issues with your debts in your individual situation (none of us know you, your circumstances, what brought you to this point, etc!) - you would be best served with some specialist advice for it, for debts in the US. The court process for debts in the US is different from that in the UK, and the US is still more complicated, because there are 50 different states involved - each of which may handle things a little bit differently. So anyone giving advice, it's important not to muddle the issue of what goes here in the UK may not be so in the US, in the relevant state. The court systems are different. And the credit reporting agencies are different - at the moment these systems are not joined up from one country to another. Whether they will be or not in the future, who can say?
For specialist, confidential,
non-judgemental advice for debts in the US, I highly recommend this organisation:
http://www.nfcc.org/It is a non-profit (charity) in the US specifically for providing debt advice to individuals such as yourself. The service they provide is either free or very low-cost - depending on what services you might utilise. The general ethos behind the organisation is one for repayment of debts, but they do look at what is the most practical & reasonable solution for the individual - be it a repayment scheme (self-administered or an organised debt management plan), bankruptcy, or some other alternative.
However, in order for anyone (a trained & qualified debt advice counsellor or otherwise) to best help you, at some point you are going to have figure out exactly who you owe & how much, etc. That would be one of the first steps.
It's tough with medical debts if there were a lot of them (which can easily happen in the US even with a single hospital stay - owing to the fragmentation of health care provision in the US) and they have since been passed from pillar to post, one debt collection agency to another, so on & so forth. You would not have been the first person who maybe didn't feel able to cope with such a situation at one point in time or another. At one time, medical debt alone was a huge portion of the bankruptcies filed in the US - and I would imagine that's probably still the case.
If you haven't been getting the mail & you're not sure who and what you owe, getting a copy of your credit reports in the US (all three of them - there are three credit reporting agencies) would be your first line of action, IMO. Someone posted a link earlier for that.
Good luck!
