DEMOCRATS' ARTICLES OF IMPEACHMENT: Did Trump obstruct congress?

< br />Democrats have officially filed their articles impeachment against President Trump, and they're accusing him of both abusing his presidential powers AND obstructing Congress. But how can the president obstruct Congress, when the Constitutional separation of powers were designed for him to do that very thing? Even Obama's DOJ said that the president and his advisors have immunity from appearing in front of a congressional committee. If the Democrats get their way and the Republicans do not truly open up everything, and they don't investigate the whistleblower, the collusion with the Democrats...if we don't undercover all of this, the Republic is deeply, deeply hurt. Because the government has three roles: providing a common defense, promoting the general welfare, and promoting domestic tranquility and right now they're doing exactly the opposite of two of those.