Well if you plan to immigrate , go for US. Because the visa system is much more complicated in UK .Also you'd need hell load of pounds to start a fresh living in UK. Start with 2500$ a month in US. I've added an extra margin to your budget since you need to look for affordable accommodation and a decent salary job.
Now I'am definitly confused , I know it's tow different countries but price can't be that different .
WhatTheGox said I need around 5000$ to stay for six months as a start (time to finda job etc ... ) and you are saying that I need 2500$ monthly or I can't live there
as I said I know he was speaking about UK and you are speaking about US but it can't be that different