If your government can waterboard people can people waterboard cats?

No. Animals at large, including cats, do not deserve to be subjected to any form of cruelty or torture. To do such an evil act would be completely deplorable.

Not only is torturing animals immoral, it is also illegal in most countries in the world.

There are many laws in place to protect the welfare of any animal, be it cats, dogs, horses, or any other species, and an act such as waterboarding would not only be illegal, and immoral, the perpetrator would also be liable to be prosecuted under the full force of the law.

Also, in many countries Waterboarding prisoners is banned as it is considered a form of torture. The United States, and all countries that are signatory to the United Nations Convention Against Torture are subject to the prohibition on torture under any circumstances.