The Stoke defender played for Wales at schoolboy level and Dragons manager Chris Coleman spoke to the Potters skipper earlier this year about switching allegiances.
However, the 25-year-old maintained England was always his first-choice despite interest from former Wales manager Gary Speed and Coleman.
“When I was a schoolboy, I played for Wales because I went to school in Wales,” said Shawcross.
“But when I turned 16, there was a rule that said I couldn’t play for Wales.
“In recent months, that rule changed and I could play for Wales again.
“But I decided years ago I wanted to play for England and I spoke to Chris Coleman, and Gary Speed before that, and made it clear that I wanted to play for England.
“So there was never any choice really.”
Shawcross, who began his career at Manchester United, is yet to make his first England appearance but the centre-half is eyeing his chance to impress.
“It’s always good to come away with the national team and now I’ve been a few times I’m starting to feel at home,” he added.
“If you’re playing well, you get noticed. At Stoke last year, we played in Europe and that got us a few headlines.
“I always felt that I had enough to hopefully break into the England squad and luckily enough I have done, so I want to stay in it.
“There’s a lot of experienced players ahead of me and it’s up to me to perform well in training. Hopefully I can play well when I get a chance.”