Valmiki Ramayana doesnt have a lot of details that other puranas cover.
There is more to surpanaka story than what is there in Ramayanaa.
Ravan's father Rishi Vishrava was son of Rishi Pulastya. He married Rishi Bharadwaj's daughtet Ilavida (devarahini) and had a son Kubera.
Pulastya was chief of Rakshas and Yaksha tribes. By the time Kubera grew up, he felt the need to consolidate all rakshas and yaksha clans and give them an independent kingdom
Vishrava suggested Lanka where Vishwakarma family built him a golden fortified city.
Kubera then got busy running the kingdom. Made it extremely prosperous and wealthy.
Vishrava stayed back in his asram but felt neglected by his son. Wife had most likely doed by then.
Kubera here made the biggest mistake of his life.
He chose his commander Rakshas Sumali's three daughters as bride for his father and sent them to him.
These three sisters were Kaikesi (Pushpotaka), Malini and Raka
All the three women had 3 sons and 1 daughter.
Kaikesi had Ravana Kumbhakarna Vibhishan and Surpanaka (Meenakshi)
Ravana when he grew up, chased kubera out of lanka with his family and became chief of Rakshas. He controlled Lanka but he established his step brothers and sisters as kings of independent kingdoms. Surpanaka was married to kalakeya Rakshas (from a region north oF himalayas) Viddyujjiva(not To confuse with her step bro who had the same name). She was widowed when Ravana attacked Kalakeyas and killed her husband. Ravana pacified her by asking her to choose a new husband. She had a son Sambukumar
Malini's children were 3 sons Mahodara, Prahasta, Khara, Mahapamsu and daughter Kumbhinasi.
These guys were given teritory south of godavari with capital at Chitrakoot Janasthan and Panchavati. Sister Kubhinasi was given as bride to king oF Mathura her son was famous Lavansur
Raka had 4 children too Trisiras, Vidyutjiva, Dusana and Tadaka (also known as Asalika)
They were given rights over land north of godavari all the way upto banks of River Ganga.
Tataka was married to Sunda a yaksha and ruled Karusha teritory (area near nagpur) She became a widow wheb Agastya killed her husband. She then ruled the kingdom with her sons Subahu and Maricha.
Kubera took refuge in the gandhamadana mountains (nepal) with rakshas and yaksha loyal to him
Now note what Rama and Lakshmana did
Before Sita was kidnapped
1. Killed Tadaka and her son Subahu under orders from Vishwamitra. Karusha then went tp suryavanshi rule
2. Came to Chitrakoot during exile killed surpanaka's son Sambukumar under the instructions of RishiS of Dandakaranya.
After this surpanaka approached Rama got mutiliated and Sita was kidnapped.
3. Then proceeded to kill Khara and his 1 brother as well as Dusan and 2 brotherS in 3 separate battles.
4. Kills Tadaka's surving son Mareech who was disguised as golden deer.
Sita gets kidnapped.
At this point Ravana has kumbhakarana Vibhishan and their sons alive along with one step brother Prahasta (Khara's brother) in Lanka and one stepsister Kumbhinasi and her family in mathura.
Rama then proceeds to kill everyone in Lanka except vibhishan and his sons who accept him as lord.
Brings back Sita.
After this Shatrughan proceeds to Mathura and kills the only other surviving family of kumbinasi, her husband and son lavanasura and occupies Mathura. Mathura goes to him and his sons
Lakshmana and his sons were given all the teritory between Narmada and Godavari.
Bharat and his sons get their mom kaikeyi's kingdom. He however annexes Gandhara too and adds to his teritory.
Surpanaka did not cause Lanka war..Rama and Lakshaman started it with Karusha kingdom, where they settle their cousins. And over a period of several years take over all the teritories of Ravana.
By the way Surpanaka Tadaka and Kumbhinasi were not just king's wife. They were independent strong women who controlled teritories of their own. Tadaka ruled Karusha.