My x-husband property was seized in 2012, by the US Marshall, I was granted a default judgement on the property on 11/12, It has been abandoned for 11 months,
High growing grass, property tax due, and place look trash, City won't touch it considering it was seized by the feds.Can I go in and squat right this property?

There is no such thing anymore as squatter's rights. It has been replaced by the law of adverse possession. Taking title to property by adverse possession has many requirements to fulfill, such as exclusively using the property for several years. However even if you could fulfill all of the requirements, adverse possession is not available against the Federal government.

If the judgment you received was against the Federal government then you would be able to take title to the property. If the judgment you received was against your ex-husband, and you received it after the US Marshall seized it, then you don't have a claim.

If you received the judgment against your ex-husband before the US Marshall seized it then you may have a case and I suggest that you speak to an attorney.

You were granted a judgment on what basis? And was this after the property had been seized by the feds? What do you mean by "city won't touch it?"

But as for trying to employ"squatter's rights" - laws vary by state but in general taking title be squatter's rights (adverse prossession) requires that you and everyone else believe and act like the property is yours, including paying taxes on it, for an extended period (like 20 years). That doesn't seem to be a viable plan here.

I'm a bit confused by this. Why was the property seized. Who granted you a judgment on property that was seized by the US Marshals? What was the judgement for?

There is a lot of gaps here.