I am applying UK standard visitor visa with family, but 2 years ago my US visa was refused. I have visited UK few years ago and Europe also. I have a good traveling history but later I tried to apply for a US visa and it got refused. Is that going to affect my UK visa application?
From this Travel.SE question information about visa refusals is shared between the UK and USA:
The route is a bit circuitous because the UK acts as a proxy for nations in the Common Travel Area...
The US and the UK are connected by the "Five Eyes Treaty".
Its impossible to say whether you will be accepted or not. You won't be rejected outright because of a previous refusal.
Answer all questions honestly. If you answer no to whether you have had previous visa refusals in other countries you could be refused under Paragraph 6 and could hold a UK entry ban:
This means that, if Deception is found, the instant application will be refused and (unless seeking to enter the UK on limited human rights grounds) the applicant will not be granted permission to return to the UK for at least 10 years.
If you answer honestly, you should not be refused just because of a previous refusal. You could still be refused of other factors, but you probably won't be refused outright because of the US visa refusal.