You've got some Constitution confusion. This is what Article V says...
"The Congress, whenever two thirds of both Houses shall deem it necessary, shall propose Amendments to this Constitution, or, on the Application of the Legislatures of two thirds of the several States, shall call a Convention for proposing Amendments, which, in either Case, shall be valid to all Intents and Purposes, as part of this Constitution, when ratified by the Legislatures of three fourths of the several States, or by Conventions in three fourths thereof, as the one or the other Mode of Ratification may be proposed by the Congress; Provided that no Amendment which may be made prior to the Year One thousand eight hundred and eight shall in any Manner affect the first and fourth Clauses in the Ninth Section of the first Article; and that no State, without its Consent, shall be deprived of its equal Suffrage in the Senate."
The Congress doesn't call a Convention, the State Legislatures do - specifically when 2/3rds of the states call for a Convention.
Amending the Constitution is - by design - extremely difficult to do. That is why after the adoption of the Constitution during the first Constitutional Convention, it has only been amended 17 times.
If Congress drafts legislation to amend the Constitution, that legislation will be voted on in the legislature and then sent to the states for ratification. I wasn’t completely off, just missing a few steps. The states can call a Constitutional Convention on their own, but if Congress drafts legislation intended to amend the Constitution, the States have to call a Convention.
Correct me if I’m wrong on any of these points, but I believe this is how I understood it in my Constitutional history class.
Yes, the states propose the convention, but if you read the clause closely it says that Congress calls the convention. Therefore, what do you do if Congress refuses to call the convention if the states ask for it? What if the Congress delays a convention indefinitely or unreasonably to manipulate election outcomes in the state legislatures?
On another note, we really ought to amend Article V to make the amending process clearer. There are a lot of very gray areas in the Article V amendment process which ought to be be amended to clarify things like how long each state has to complete the ratification of an amendment, whether a state can withdraw its ratification once they've given it as long as the amendment isn't ratified yet, whether a state can change its vote from no to yes. What happens when the US uses the military to compel states to ratify (like in the Civil War which also rigged the state legislatures with the rump legislatures)? Who gets to determine when the ratification has been properly done? What if states are added in the middle of a ratification process, do you use 3/4 of states at the time it was proposed or 3/4 the number of states at the end of the process? etc. All of these are real questions that have come up at some point of US history. The amendment sounds so straight forward when you read Article V, but in reality there are some serious problems. It could use a little clarification.