“Can I justify following this training to my American colleagues?”
You become clearer and faster in your communication. They will understand you better. I think they will appreciate that.
Americans will realize that what you are proposing is good for this market with these demanding customers. They get a clear and positive impression of you. They get access to your expertise. They notice that you contribute ideas. They feel helped by you. They get the feeling that they can trust you and that you solve problems. They can leave more to you.
Making good proposals is in the interests of yourself, the Americans, your company, project, future and your pleasure in the job.
Even if your colleague might be a little upset, feel and explain that you have the right intentions. He or she will soon experience the difference as you will manage to bridge gaps. By learning more about the American culture, you will learn more about yours, your past reactions, your new ones, etc. You will become better and better.
(Some Americans might consider us ‘weepers’ now, very negative, opinionated or extremely vague at times. “What exactly do they want to say? What do they want to achieve? They are slow. They put our chance to win and our profit at risk.” You want to prevent that image because it is based on labels and misunderstanding and will damage your cooperation.)